Molecular structures and vibrational frequencies of 2-, 3- and 4-pyridine carboxaldehydes by ab initio Hartree–Fock and density functional theory calculations

AbstractThe molecular structures, vibrational frequencies, and corresponding vibrational assignments of 2-amino-3-, 4-, and 5-nitropyridine have been calculated by using ab initio Hartree-Fock (HF) and density functional theory (B3LYP) methods with 6-311++G(d,p) basis set level. The calculated vibrational frequencies and optimized geometric parameters (bond lengths and bond angles) were found to be in well agreement with the experimental data. The comparison of the observed and the calculated results showed that the scaled B3LYP method is superior to the scaled HF method for both the vibrational frequencies and the geometric parameters. For well fitting the calculated and the experimental frequencies we used scale factors obtained from the ratio of the frequency values of the strongest peaks in the calculated and the experimental spectra. These obtained scales seem to cause the better agreement of the gained vibrations to the experimental data.

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Theoretical molecular structures for partially bonded complexes of trimethylamine with SO2 and SO3: ab initio and density functional theory calculations

Journal of Molecular Structure THEOCHEM ◽

10.1016/s0166-1280(02)00262-2 ◽

2002 ◽

Vol 594 (3) ◽

pp. 147-156 ◽

Cited By ~ 5

Author(s):

Jaebum Choo ◽

Sunghwan Kim ◽

Younghi Kwon

Keyword(s):

Density Functional Theory ◽

Ab Initio ◽

Density Functional ◽

Density Functional Theory Calculations ◽

Molecular Structures ◽

Functional Theory ◽

Bonded Complexes

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Conformational and Vibrational Analysis of 2,4-, 2,5- and 2,6-Difluorobenzaldehydes by ab initio Hartree-Fock and Density Functional Theory Calculations

Zeitschrift für Naturforschung A ◽

10.1515/zna-2008-3-410 ◽

2008 ◽

Vol 63 (3-4) ◽

pp. 175-182 ◽

Cited By ~ 3

Author(s):

Adnan Sağlam ◽

Fatih Ucun

Keyword(s):

Density Functional Theory ◽

Ab Initio ◽

Density Functional ◽

Vibrational Analysis ◽

Molecular Structures ◽

Basis Set ◽

Functional Theory ◽

Vibrational Assignments ◽

Hartree Fock ◽

The Mean

The optimized molecular structures, vibrational frequencies and corresponding vibrational assignments of the two planar O-cis and O-trans rotomers of 2,4-, 2,5- and 2,6-difluorobenzaldehyde have been calculated using ab initio Hartree-Fock (HF) and density functional theory (B3LYP) methods with the 6-311++G(d,p) basis set level. The calculations were adapted to the CS symmetries of all the molecules. The O-trans rotomers with lower energy of all the compounds have been found as preferential rotomers in the ground state. The mean vibrational deviations between the vibrational frequency values of the two conformers of all the compounds have been shown to increase while the relative energies increase, and so it has been concluded that the higher the relative energy between the two conformers the bigger is the mean vibrational deviation.

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